package com.rmb.util;

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import org.apache.commons.codec.binary.Hex;
/**
 * @author ZhaoMyYang
 */
public class JavaDsa {

    private static String src = "Can I help you?";

    public static void main(String[] args) throws Exception {
        jdkdsa();
    }

    public static void jdkdsa() throws Exception{

        //1.初始化密钥
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DSA");
        keyPairGenerator.initialize(512);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        DSAPublicKey dsaPublicKey = (DSAPublicKey) keyPair.getPublic();
        DSAPrivateKey dsaPrivateKey = (DSAPrivateKey) keyPair.getPrivate();

        //2.执行签名【私钥签名】
        PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(dsaPrivateKey.getEncoded());
        KeyFactory keyFactory = KeyFactory.getInstance("DSA");
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
        //SHA1WithDSA
        Signature signature = Signature.getInstance("SHA1WithDSA");
        signature.initSign(privateKey);
        signature.update(src.getBytes());
        byte[] result = signature.sign();
        System.out.println("JDK实现DSA数字签名：" + Hex.encodeHexString(result));

        //3.验证签名【公钥验证】
        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(dsaPublicKey.getEncoded());
        keyFactory = KeyFactory.getInstance("DSA");
        PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
        signature = Signature.getInstance("SHA1WithDSA");
        signature.initVerify(publicKey);
        signature.update(src.getBytes());
        boolean bool = signature.verify(result);
        System.out.println("数字签名有效？" + bool);
    }


}
